tapply(x, y, min) where x is the vector of numbers and y the vector of class labels.
Best, -- Wolfgang Viechtbauer http://www.wvbauer.com/ Department of Methodology and Statistics Tel: +31 (0)43 388-2277 School for Public Health and Primary Care Office Location: Maastricht University, P.O. Box 616 Room B2.01 (second floor) 6200 MD Maastricht, The Netherlands Debyeplein 1 (Randwyck) ________________________________________ From: r-help-boun...@r-project.org [r-help-boun...@r-project.org] On Behalf Of Waverley @ Palo Alto [waverley.paloa...@gmail.com] Sent: Thursday, October 29, 2009 6:47 AM To: r-help Subject: [R] how to fetch rows with certain characteristics Hi, I have a matrix, first column is of certain values, second column is the class labels or a factor. e.g. 1.2 1 1.3 1 1.3 1 1.5 1 2.1 2 2.0 2 9.9 2 1.4 3 1.8 3 1.9 3 I want to find out what is the min values of column 1 for each corresponding class (column 2). For the above example, I want to return a matrix of 1.2 1 2.0 2 1.3 3 Can someone suggest how to code for that? The second column can be of characters. Thanks much. -- Waverley @ Palo Alto ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
